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20 June 2007


Toshiba’s CMOS single-chip 60GHz millimeter-wave receiver challenges GaAs

At last week’s 2007 Symposia on VLSI Circuits, in Kyoto, Japan, Tokyo-based Toshiba Corp unveiled low-cost 90nm silicon-based complementary metal-oxide semiconductor (CMOS) process technology that enables the manufacturing of highly integrated, single-chip ICs for high-speed millimeter-wave wireless communications at 60GHz over short distances.

Millimeter-wave communication offers high-speed wireless communication in the 60GHz band (a frequency over ten times higher than that of wireless local-area networks). Communication distances are limited to a few meters, but the wide bandwidth of the signal allows data transfers at a rate of more than 1Gbit/s.

In Japan, the US and Europe, frequencies around the 60GHz band are allocated to unlicensed equipment. In Japan, the allocated range is 59-66GHz (a bandwidth of 7GHz, enough for high-speed data transmission). So, driven by the confluence of broadband digital content and wireless home networks, interest in millimeter-wave communication is increasing as a solution for short-range, high-speed wireless transmission of data such as high-definition video between digital equipment in the home.

Millimeter-wave communications ICs operating at 60GHz are traditionally fabricated in gallium arsenide, requiring the separate integration in a module of an antenna and a synthesizer (which can not be fabricated using GaAs), leading to increased cost and chip die size (compared to silicon-based CMOS), says Toshiba.

But, with advances in process technology, CMOS is now approaching a level where it is applicable to the millimeter waveband, Toshiba says. In particular, the use of 90nm CMOS process technology supports high levels of integration and achieves a performance close to that of more complex GaAs devices, the firm claims.

Toshiba has hence fabricated a demonstration 60GHz CMOS receiver chip that integrates all required receiver function blocks - an antenna, low-noise amplifier, a mixer, and a phase-locked loop (PLL) synthesizer - in a die that is only 1.1mm x 2.4mm (without pad area). Fully differential circuitry (including a differential on-chip dipole antenna) improves signal quality, as it achieves noise-resistant features suited to millimeter-wave IC application. Optimization of the element structure and wiring structure constrains the internal noise, and has contributed to realizing stable operation (which is the major issue to be overcome for millimeter-wave CMOS ICs).

Toshiba says that, as well as continuing to improve the integration and performance of the receiver IC, it aims to develop the high-power technology needed for a transmitter IC, targeting the practical application of a single-chip millimeter-wave CMOS transceiver IC.